Asteroid 4769 Castalia is a near-Earth crossing asteroid that was
discovered by Eleanor F. Helin (Caltech) on August 9, 1989. Scientists
used radio astronomy and computer modeling to generate this image of
Castalia. They obtained the data for the computer model in 1989 using
the Arecibo radar/radio telescope in Puerto Rico when the asteroid
passed within 5.6 million kilometers (3.5 million miles) of the Earth.
R. Scott Hudson (Washington State University) and Steven J. Ostro (JPL)
used the detailed time-delay and Doppler data from the radio echos to
produce this 3D computer model.

Castalia has a dumbell shape and is about 1.8 kilometers (1.1 miles)
across at its widest. Its two distinct lobes are about .75 kilometers
(.47 miles) across. It has a narrow waist of approximately 100 to 150
meters (330 to 490 feet) in depth. The two lobes were probably separate
objects that came together after a relatively gentle collision. The
surface of both lobes have similar composition and roughness. The
effective resolution of the reconstruction is about 100 meters (330
feet). This is the first detailed 3D model of a near Earth asteroid yet
produced, and the most conclusive evidence to date of a "contact-binary"
object in the solar system.

Castalia
This view of Castalia shows one of 16 different views of a 3D computer
model. All 16 views can be obtained by selecting this image.
(Courtesy NASA/JPL)

Topographic Map of Castalia
This is a topographic map of Castalia. It is based upon the shape model of Phil
Stooke which he produced using rendered images of the shape model by R.S. Hudson
and S.J. Ostro. As with all maps, it is the cartographer's interpretation;
not all features are necessarily certain given the limited data
available. This interpretation stretches the data as far as possible.
(Courtesy A. Tayfun Oner)

Shaded Relief Map of Castalia
This image is a shaded relief map of asteroid 4769 Castalia, previously
known as 1989 PB. As with all maps, it is the cartographer's
interpretation and not all features are necessarily certain given the
limited data available. This interpretation stretches the data as far as
is feasible.
(Courtesy Phil Stooke)

Cylindrical Map of Castalia
This is a shaded relief map of asteroid 4769 Castalia, previously known
as 1989 PB. It is the same map as in the above image, but reprojected
to a Simple Cylindrical map. As with all maps, it is the cartographer's
interpretation and not all features are necessarily certain given the
limited data available. This interpretation stretches the data as far
as is feasible.
(Courtesy Phil Stooke)